75 research outputs found
Estimation and quantification of liver iron concentration by magnetic resonance imaging
Background: Liver iron overload is considered to be the histological hallmark of genetic hemochromatosis. The accurate estimation of iron overload is important to establish the diagnosis of hemochromatosis. The aim of the present study was to estimate T2* liver value, quantify liver iron concentration (in milligram of iron per gram dry weight) and find out the appropriate therapy for patients with iron overload according to severity index.Methods: A cross-sectional observational study was carried out in Department of Radio Diagnosis, at B.Y.L. Nair Hospital and medical college, Mumbai from June 2017 to August 2018. A total of 50 cases were enrolled for the present study.Results: Male predominance (66.0%) was seen. Mean duration of disease among the studied cases was 10.52±6.06 years, with minimum and maximum duration of disease of 1 and 26 years respectively. Eight percent had compliance to visit and treatment among the enrolled cases.Conclusions: MRI was concluded to be potentially useful non-invasive method for evaluating liver iron stones in a wide spectrum of haematological and liver diseases
Predicting and grading the degree of difficulty of cochlear implant surgery by evaluating temporal bone using high resolution computed tomography and magnetic resonance imaging
Background: The current study was designed to assess the challenges that arise during cochlear implantation. Hence imaging based grading system, using a structured, 12-point scoring chart was developed with an aim to assess various anatomical factors of temporal bone helpful in contemplating complications involved in surgery and to assess various congenital and acquired abnormalities if detected during scan which can affect cochlear implant surgery.Methods: This was a descriptive study done on 60 patients with sensorineural hearing loss. They were evaluated preoperatively by using HRCT and MRI findings and subsequently underwent cochlear implantation. A 12-point scoring chart was developed based on imaging findings. Surgical times were noted in each case and each imaging point on the scoring chart was correlated with the surgical times.Results: Eleven out of 12 points in the scoring chart proved to be statistically significant in predicting the degree of difficulty of the surgical procedure. One point was not correlating with the surgical timings. Based on the grading system, in the present study, there were 37 patients (61.66%) classified as Grade 1, 16 patients (26.67%) classified as Grade 2 and 7 patients (11.67%) classified as Grade 3.Conclusions: These radiological image findings and its related grading system are relatively easy and quick to assess on readily available pre-operative temporal bone CT scan and MRI. They can form a pre-operative checklist that provides a formalized approach for the surgeons and, in particular surgical trainees, predict and, thus prepare for, potentially challenging cochlear implant cases
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Numerical Determination of Temperature Profiles in Flowing Systems From Conversions of Chemically Reacting Tracers
This study presents the mathematical bases of the measurement of internal temperatures within flowing systems using chemically reacting tracers. It considers plug-flow (or piston-flow) systems. The differential equation for reactant conversion can be reformulated into a Fredholm integral equation of the first kind. In the Fredholm integral equation the unknown is the temperature distribution function, which characterizes the internal temperature profile of the flowing system. Due to nonlinearity of the kernel, the usual technique of regularization has been modified into an iterative approach. This new approach is employed to solve this Fredholm integral equation. The iterative approach successfully overcomes the usual difficulty of determining the optimal value of the regularization smoothing parameter. Advantages and disadvantages of this method are discussed, and the results are compared with those obtained by optimization of undetermined parameters in a postulated temperature distribution function. The insight acquired from this study can be used to determine temperature profiles for many existing systems, and can form a basis for analysis of the more complicated dispersed-flow systems. The iterative Fredholm integral equation method is tested to see what is required to discriminate between two models of the temperature behavior of Hot Dry Rock geothermal reservoirs. It is found that using as few as two reacting tracers can distinguish between the models and provide a reasonable approximation of the temperature profile within a reservoir. 10 refs., 6 figs., 2 tabs
Stable Polymorphs Crystallized Directly under Thermodynamic Control in Three-Dimensional Nanoconfinement: A Generic Methodology
Polymorphism: an evaluation of the potential risk to the quality of drug products from the FarmĂĄcia Popular Rede PrĂłpria
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Generation and cyclization of nitrilium ions from amides and synthesis of chiral amines
Part I. Cationic cyclization reactions of unsaturated amides were studied. Several different unsaturated amides were prepared and their ability to undergo cyclization in refluxing PPSE was examined. A successful cyclization afforded 5-membered nitrogen heterocycle (pyrroline derivatives). The best results were obtained with unsubstituted amides. The conditions are compatible with esters, halides, and ethers. The cyclization reactions failed when electron withdrawing groups were placed on the -carbon of the amides. Enantiomerically enriched indolizidine ring systems were prepared by asymmetric reduction of pyrroline esters, obtained from cyclizations of amide esters.Part II. trans-1,3-Dibenzyl isoindoline, an amine bearing a C\sb2 axis of symmetry, was prepared using a chiral auxiliary. Use of chiral auxiliaries in asymmetric synthesis of acyclic amines was investigated
Optimal Catalyst Activity Profiles In Pellets .7. the Case of Arbitrary Reaction-kinetics With Finite External Heat and Mass-transport Resistances
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Using conversions of chemically reacting tracers for numerical determination of temperature profiles in flowing systems and temperature histories in batch systems
This report presents the mathematical bases for measuring internal temperatures within batch and flowing systems using chemically reacting tracers. This approach can obtain temperature profiles of plug-flow systems and temperature histories within batch systems. The differential equations for reactant conversion can be converted into Fredholm integral equations of the first kind. The experimental variable is the tracer-reaction activation energy. When more than one tracer is used, the reactions must have different activation energies to gain information. In systems with temperature extrema, multiple solutions for the temperature profiles or histories can exist, When a single parameter in the temperature distribution is needed, a single-tracer test may furnish this information. For multi-reaction tracer tests, three Fredholm equations are developed. Effects of tracer-reaction activation energy, number of tracers used, and error in the data are evaluated. The methods can determine temperature histories and profiles for many existing systems, and can be a basis for analysis of the more complicated dispersed-flow systems. An alternative to using the Fredholm-equation approach is the use of an assumed temperature- distribution function and incorporation of this function into the basic integral equation describing tracer behavior. The function contains adjustable parameters which are optimized to give the temperature distribution. The iterative Fredholm equation method is tested to see what is required to discriminate between two models of the temperature behavior of Hot Dry Rock (HDR) geothermal reservoirs. Experimentally, ester and amide hydrolyses are valid HDR tracer reactions for measuring temperatures in the range 75-100{degrees}C. Hydrolyses of bromobenzene derivatives are valid HDR tracer reactions for measuring temperatures in the range 150-275{degrees}C
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